fs getfid defaults to '.', like other path-related commands

fs getfid defaults to '.', like other path-related commands

I noticed that all of the other commands that accept a list of paths
use the SetDotDefault() function to default to ".", when no arguments
are given.  This patch adds that call to getfid, making it more
consistent with similar commands.

Change-Id: Ia50c6805996d338cbd8d006107caa4ea56178c8e
Reviewed-on: http://gerrit.openafs.org/3008
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>